The household power meter dates back to the early 1870’s and has been an often overlooked device. No one is at fault really, it sits outside, out of sight and out of mind. Various improvements have been made over the years to “watt hour meters” as they’re called but generally they have only been incremental improvements. The technology started with Samuel Gardiner and his DC lamp hour meter (it really was a clock with an electromagnet) to improvements in AC with Galileo Ferraris’ induction-type watt hour meter and onto Westinghouse’s “polyphase” meters. Improvements made them more accurate and smaller but they could be better… of course.
This is where the REX2 comes in, small and unimposing and able to wirelessly transmit usage data. Right off the bat it’s an improvement because it eliminates the need for someone to come by and check it. That’s a lot of saved fossil fuels! There have been worries that smart power meters might cause health problems though. These worries would have ground to stand on if not for the fact that the REX2 only transmits every six hours for 40 milliseconds. Couple that with a specially designed antenna that forces signals away from the home and it can be reasoned that these devices are safer than carrying a cell phone in your pocket.
The Elster REX2 has a relatively simple set of internal components. Running the LCD display is a Teridian 71M6531F with SoC and an MPU core. Handling the power needs of the device are two chips. A Texas Instruments LM2904 low power dual operational amplifier and a RMFD RF2172 medium power amplifier. That specially designed RF antenna mentioned earlier is connected to a Texas Instruments CC1110F32 low power SoC MCU that runs sub 1GHz. Signals are encrypted and sent on the 900 MHz ISM band using a “controlled mesh” network. A “controlled mesh” network is essentially a city full of REX2’s all communicating with each other to relay power readings to a gateway device. The gateway device in turn sends the data to the power company.
It seems like natural progression to have wireless smart meters keeping tabs on our power use. After all, how would we see the savings in smart home integration? Surely not one of those old mechanical meters with rotating wheels.